The present invention relates to soil processing, and more particularly, to a processor for reclaiming the so-called "root medium" over acreage which has been surface mined.
During such surface mining, sometimes called strip mining, wherein overburden is displaced by sometimes immense machinery for recovering coal or other minerals below the surface, massive amounts of earth are displaced resulting in a layer of spoil many feet deep which, because of the stripping operation, has incorporated into it large rocks, roots, logs and other coarse debris. Following such surface mining, it is desired to reclaim the mined acreage to provide a top layer of several feet in depth consisting of texture (including soil, dirt, mixed medium including rock or other objects not larger than a certain size) which is then to be covered by a layer of topsoil. Thus, there may be four feet of texture covered by an additional one foot depth of topsoil, and together constituting the "root medium". In reclaiming the root medium, it has heretofore been required to use large earth moving equipment, including rubber-tired equipment as well as crawler tractors. Such equipment is used for removing rock and other undesired objects larger than a predetermined dimension, such as 10 in..sup.2, such large objects may not be permitted in the texture portion of the root medium, and no rock may be permitted within the top soil layer, which may be termed the "plow zone".
It has been found that such earth moving equipment is very cumbersome for reclaiming operations, and presents difficulties including ineffective removal of rock and other large objects. There is a tendency for scraper blades and the like to become jammed and damaged by objects, particularly large rock for example. In using rake-type equipment, a common problem is that rocks or debris are "stirred" and frequently are lost from in front of the rake, being incorporated back into the root medium.
Another problem is the compaction of the root medium because of the weight and continued travel over the root medium by such earth moving equipment. Concerning compaction, it may be assumed that undisturbed acreage suitable for farming will have a compaction of not greater than about 68%. When the root medium of reclaimed acreage is compacted by earth moving equipment, approaching a maximum compaction of 100%, roots of row crops will not penetrate the root medium, and such compaction must be alleviated if the reclaimed land will be utilizable for prime agricultural purposes. To overcome the compaction problem, it has been attempted to utilize conventional rippers, as well as rock or root rakes. Such apparatus may be towed or pushed to drag deeply submerged cutting or lifting elements through the soil being reclaimed. The use of such equipment is itself detrimental, as it is itself causative of compaction, but primarily is objectionable because it necessitates an expensive and equipment-intensive operation which it would be desirable to avoid.
In general, there has not existed any aparatus, machine or combination thereof for satisfactorily eliminating foreign materials and objects from acreage to be reclaimed as well as for avoiding undesirable compaction. Further, existing conditioning equipment has relied upon lifting and overturning large amounts of soil, requiring powerful equipment with accompanying high cost and full consumption.